Two fundamentally different switching technologies exist that enable digital communications. First, circuit switching technology utilizes dedicated lines or channels to transmit data between two points, similar to public switched telephone networks (PSTN). The second, packet switching technology, utilizes a "virtual" channel to establish communications between two points. The virtual communication channel is shared by multiple communication processes simultaneously and is only utilized when data is to be transmitted. Since the differing performance requirements for voice transmission and data transmission impose different design priorities, historical development of voice communication systems such as the telephone, and its related business systems, such as a corporate business telephone system, e.g. Public Branch Exchange (PBX) and Automatic Call Distribution (ACD), has centered on circuit switching technology. Conversely, data communication systems, such as Local Area Networks (LANs), Wide Area Networks (WANs) and the Internet have primarily relied upon packet switching technology. As a result, separate cultures and networking fabrics have evolved for the design, development, application, and support for real-time voice communications (circuit switched networks) and non real-time data transmission (packetized data networks).
Recently, attempts have been made to utilize packetized data networks for voice transmission with only limited success. One reason is that high quality, real-time interactive voice communications must emulate a reasonable approximation of a face to face conversion between two geographically separated people. To accomplish this, the modulated signal representing the spoken words should (i) have enough information to re-create a recognizable voice by using a fixed bandwidth, (ii) be delivered with minimum delay by using a dedicated path in order not to impede interactive communications, (iii) be delivered at a constant rate in order to avoid distortion to the ear of the listener and (iv) not be subject to significant loss of information en route. These capabilities are inherent in circuit switched networks such as the public switching telephone network (PSTN) but must be created when using packetized data networks for voice transmission.
The design of private "Intranets". e.g. LANs and WANs, and the Internet is fundamentally different from the architecture of conventional voice transmission networks. Packetized data networks break down data, e.g. a voice signal, into a series of small, discrete packets for transmission. Each packet of data travels independently through the network to the destination address where application software reassembles the packets to recreate the original data set. As currently designed, packetized data networks handle congestion by discarding or delaying packets or by sending packets from the same source along different pathways, often resulting in packets sequences arriving out of order. If the transmitted data packet represents real-time voice, the listener may perceive a gap or "choppiness" as a result of missing, late-arriving or out-of-sequence packets.
As the work environment increasingly demands faster access to greater volumes of information from multiple sources, the individual capabilities of separate circuit switched and packetized data networks are being seriously challenged. The response from circuit switch manufacturers has been the development of new switching system architectures that make it easier for separate, application-specific software to control the circuit switching function, and to seek to maintain the market value of circuit switched systems by increasingly using voice application processes to offer additional services such as voice mail, interactive voice response and ACD. The intensity of technical activity involved in further integrating the interaction of specific application processes and information delivery systems has given computer telephony integration the status of a technology in its own right.
A growing number of businesses and other organizations have recognized the Internet as a network which enables an enhanced form of public communication. In order to create conditions amenable to satisfactory commerce and business communications on the Internet, the same communication services offered via traditional voice transmission networks, such as the PSTN, must be available when communicating with customers via the Internet.
The introduction and rapid development of Internet Protocol ("IP") technology revolutionized the deployment and use of data communications networks such as the Internet. Even though this technology is in its infancy, it is already creating a growing demand for the integration of features and functions available in traditional voice communications networks into the packetized data network environment. The Internet represents primarily an access to potential markets that cannot be efficiently exploited if a separate, parallel infrastructure is required for its service.
Accordingly, it is an object of the present invention to provide a virtual switching architecture which enables packet-switched networks to provide functionalities similar to circuit switched networks and to interface with communications originating to and from circuit switched networks in a meaningful manner.